ScriptJunkie:
My question to you is: Are you sure you want to do that? Why would you want to do that? Are you selling dollar items with a minimum purchase amount?
Beyond that, you might want to think it over carefully. Customers are funny about being told what they must purchase. Personally, if I went to a site and they wouldn't allow me to purchase only what I wanted without forcing me to buy more, not only would I leave without making a purchase, but I would not return.
As an alternative, you might consider either setting product minimums per product on some of your lower cost items, or raising your prices to make a sale worth your cost involved in doing business.
Remember, any sale is a good sale, and empires are built from pennies. It's never good to risk alienating a potential customer.
I follow your reasoning. And some items I use the minimum item feture. However, that might be a great strategy for a different business but not in my side of the Aquarium hobby :0) You see, I sell live plants, fish and shrimp for a subset of the aquarium hobby that focuses on growing bonzai-like gardens in aquariums. Individual live plants may cost as little as $0.60 yet the packaging and handling to ship them is costly (think cold pack, foam insulation, sorting and you get the picture). Forcing mandatory minimums on every item narrows customer base. It would be fine if everyone started out with a 100 gal aquarium and would buy 12 orders each of 50 different plants but they don't.
Having an overall minimum order amount is accepted in our world so we don't lose money spending $6 in labour for packing $5 in plants. In my case, my min order for my old site was $25. If I raised the price on all my items, I would be selling the most expensive plants compared to competitors.